Matplotlib graphic image to base64

Question

Problem : Need to transform a graphic image of matplotlib to a base64 image

Current Solution : Save the matplot image in a cache folder and read it with read() method and then convert to base64

New Problem : Annoyance : Need a workaround so I dont need to save the graphic as image in any folder. I want to just use the image in the memory. Doing unnecessary I/O is a bad practice.

def save_single_graphic_data(data, y_label="Loss", x_label="Epochs", save_as="data.png"):
    total_epochs = len(data)
    plt.figure()
    plt.clf()

    plt.plot(total_epochs, data)

    ax = plt.gca()
    ax.ticklabel_format(useOffset=False)

    plt.ylabel(y_label)
    plt.xlabel(x_label)

    if save_as is not None:
        plt.savefig(save_as)

    plt.savefig("cache/cached1.png")

    cached_img = open("cache/cached1.png")

    cached_img_b64 = base64.b64encode(cached_img.read())

    os.remove("cache/cached1.png")

    return cached_img_b64

Asked By: KenobiBastila

||

Source

Answer 1

import cStringIO
my_stringIObytes = cStringIO.StringIO()
plt.savefig(my_stringIObytes, format='jpg')
my_stringIObytes.seek(0)
my_base64_jpgData = base64.b64encode(my_stringIObytes.read())

[edit] in python3 it should be

import io
my_stringIObytes = io.BytesIO()
plt.savefig(my_stringIObytes, format='jpg')
my_stringIObytes.seek(0)
my_base64_jpgData = base64.b64encode(my_stringIObytes.read())

I think at least … based on the documentation http://matplotlib.org/api/pyplot_api.html#matplotlib.pyplot.savefig

Answered By: Joran Beasley

Answer 2

For python 3

import base64
import io 
pic_IObytes = io.BytesIO()
plt.savefig(pic_IObytes,  format='png')
pic_IObytes.seek(0)
pic_hash = base64.b64encode(pic_IObytes.read())

The reason is both cStringIO and cStringIO.StringIO() are deprecated

Answered By: BoyePanthera

Answer 3

I could not get answers above work, but this did:

    import io
    import base64
    s = io.BytesIO()
    plt.plot(list(range(100)))
    plt.savefig(s, format='png', bbox_inches="tight")
    plt.close()
    s = base64.b64encode(s.getvalue()).decode("utf-8").replace("n", "")
    return '<img align="left" src="data:image/png;base64,%s">' % s

Answered By: Rex D

Matplotlib graphic image to base64

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